Satoru Yada

Potential bile acid metabolites. 24. An efficient synthesis of carboxyl-linked glucosides and their chemical properties.

A facile and efficient synthesis of the carboxyl-linked glucosides of bile acids is described. Direct esterification of unprotected bile acids with 2,3,4,6-tetra-O-benzyl-d-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the α- and β-anomers (ca. 1∶3) of the 1-O-acyl-d-glucoside benzyl ethers of bile acids, which was separated effectively on a C18 reversedphase chromatography column (isolated yields of α- and β-anomers are 4–9% and 12–19%, respectively). Subsequent hydrogenolysis of the α- and β-acyl glucoside benzyl ethers on a 10% Pd−C catalyst in acetic acid/methanol/EtOAc (1∶2∶2, by vol) at 35°C under atmospheric pressure gave the corresponding free esters in good yields (79–89%). Chemical specificities such as facile hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed.

Thermal Decomposition Products of Phthalates with Poly(vinyl chloride) and Their Mutagenicity

The thermal decomposition of phthalate alone and with poly(vinyl chloride) (PVC) was carried out under a nitrogen atmosphere in a 4-necked separable flask. The thermal decomposition of phthalate in the presence of PVC began at 150°, about 100°C lower than the decomposition of phthalate alone. The formation of octyl chloride indicated an interaction reaction between phthalate and PVC. From the analysis of the composition of commercially plasticized PVC sheet (film and board), the phthalates (dibutyl phthalate, dihexyl phthalate) and di(2-ethylhexyl) phthalate), 2-ethyl-1-hexanol, phthalic anhydride, and 2-ethylhexyl hydrogen phthalate were identified. The mutagenicities of these decomposition products were higher than those of phthalic diesters (phthalates).

Comparative studies of homogeneous and heterogeneous catalyses: Part III. The hydrogenation of disubstituted cyclohexenes over Rh and Rh(PPh3)3Cl

Abstract The homogeneous and heterogeneous hydrogenations of methyl 4-t-butyl -1-cyclohexenyl ether (I), methyl 4-t-butyl-1-cyclohexenyl ester (II) and methyl 4-t-butyl-1-methylcyclohexene (III) over Rh and Pd metals and the Rh metal complex catalyst, RhCl(PPh3)3, are reported. The isomer distributions of products formed from I, II and III are compared for the homogeneous and heterogeneous catalytic hydrogenations. The hydrogenations of I, II and III over Rh metal catalyst give mainly the cis isomer for I and II, whereas the trans isomer is formed in large excess over the Rh metal complex. The implications of these stereochemical results for the mechanism are examined on the basis of the exchange patterns obtained during the deuteration of the substrates, as well as on the basis of various kinetic factors. In addition, the effects of the solvent and the ligands of the Rh complex catalyst on the stereochemistry of hydrogenating II have been investigated. The trans isomer is obtained in 93% yield when o-cresol is used as the solvent. The Rh complex containing the dimethylaminophenylphosphine ligand gives the largest amounts of trans isomer (93%).